Mechanical properties

An indentation test has been employed to evaluate the mechanical properties of Anatolian obsidian. Different fracture modes are observed during Vickers indentation as it is shown by residual damages. The influence of the chemical composition of the volcanic glasses on its hardness and brittleness is discussed, and, the notion of densification/shear is proposed as an important factor in the behaviour of obsidian under physical stress. To complement, these scratch tests were employed to identify three regimes of deformation of obsidian: micro-ductile (zone 1), micro-cracking (zone 2) and microabrasive (zone 3) regimes. These experiments lead us to develop a numerical model of the indentation test, established in the finite element code ABAQUS/Explicit. The model allowed  us to investigate the effect of the increase  the crack propagation during indentation test (elastoplastic behaviour).

This approach allowed us to propose an initial classification of different Anatolian obsidians in terms of their mechanical properties. We discuss of the influence of geochemistry on the evolution of damage, friction and deformation. In this study, obsidian from the three main sources exploited in the Neolithic have been investigated: Göllü Dağ and Nenezi Dağ, in Central Anatolia and, Çavuslar in the Bingöl region (Eastern Anatolia).

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